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Biomedical subjects

G Michelson

Publications and source records attributed to G Michelson.

50 records · Page 3Linked to original sources
PubMed1991

O2 administration by a nasal probe improves respiration in cataract surgery after retrobulbar anesthesia.

We measured certain respiratory conditions (respiratory rate [RR], oxygen saturation [SO2], and end-expiratory carbon dioxide partial pressure [pCO2]) of 31 patients undergoing planned cataract surgery using local anesthesia in order to determine the effects of administering pure oxygen (3 L/min) by a nasal probe in 10 of them. In the patients who did not receive pure oxygen, at the end of surgery the mean RR was 15.8 +/- 4.4/min (maximum, 21; minimum, 6.4/min); the mean SO2 was 86.9% +/- 6.6% (maximum, 98%; minimum, 74%; in 11/25 patients, the SO2 was lower than 90%); and the mean pCO2 was 34.9 +/- 7.7 mm Hg (maximum, 46.5; minimum, 12.15; in 4/25 patients, the pCO2 was greater than 45 mm Hg). In the patients who received pure oxygen by a nasal probe, the mean SO2 increased intraoperatively from 80.6% +/- 5.8% to 96.9 +/- 2.9% (in no patients was SO2 lower than 90%). Therefore we recommend an intraoperative administration of pure oxygen by a nasal probe.

Administration, Intranasal↗
PubMed1990

Regulation of rat ileal water absorption by central alpha 2 adrenergic receptors.

This study examined the role of central adrenergic receptors in the regulation of water absorption by the rat ileum. Clonidine, an alpha 2-adrenergic receptor agonist, increased water absorption in vivo following intracerebroventricular but not intravenous injection. Intracerebroventricular injection of prazosin, an alpha 1-adrenergic receptor antagonist, did not alter basal water absorption. Prazosin did not prevent the clonidine effect. In contrast, the alpha 2-adrenergic receptor antagonist, yohimbine, reduced basal absorption and prevented the intracerebroventricular clonidine effect. Treatment with reserpine reduced ileal norepinephrine content by 98%, reduced basal water absorption consistent with a loss of sympathetic outflow to the mucosa, but did not prevent the increase in water absorption due to intracerebroventricular clonidine. These results suggest that central alpha 2 receptors regulate water absorption by the rat ileum. The clonidine-induced increase in water absorption is not mediated by the sympathetic nerves innervating the intestine.

Absorption↗
PubMed1990

Experimental autologous inverse keratoplasty--epithelial, stromal and endothelial interactions.

After the reversal of a 4-mm central corneal button in 20 rabbits, no epithelial proliferation was observed in the anterior chamber. The epithelium and the wound margins facing the anterior chamber were covered by a large fibrin clot, which suppressed epithelial cell growth and served as a matrix for rapidly proliferating fibroblasts while apparently stimulating their growth. The inverted epithelium was overgrown by stromal tissue and eventually disappeared. Fibrous proliferation ceased after tissue had been covered by corneal endothelium. We suggest that fibrin clotting and stromal fibroblastic proliferation are important factors that prevent epithelial growth on the inner corneal surface.

Animals↗
PubMed1990

[Pulsed Doppler ultrasonography of the ophthalmic artery in proliferating diabetic retinopathy].

In 19 patients with bilateral proliferative diabetic retinopathy we examined the blood velocity in the ophthalmic artery with pulsed ultrasound and analyzed the outline of the pulse curve with the fast fourier transformation. The data were compared with the results in 50 normal objects. Patients with diabetic proliferative retinopathy showed increased systolic blood velocities (p less than 0.05), decreased diastolic blood velocities (p less than 0.05) and an alteration in the outline of the pulse curve (p less than 0.001). These changes can be due to diabetic-induced decrease in the elasticity of the wall of the ophthalmic artery and to microangiopathic alterations in the choroid. In some patients in the course of the ophthalmic artery, we saw localized peaks in the blood velocity, which can be interpreted as local stenosis in the ophthalmic artery.

Aged↗
PubMed1990

Blood velocity in the ophthalmic artery in normal subjects and patients with endophthalmitis.

Some ocular diseases lead to temporary changes in the ocular blood circulation. This study was undertaken to evaluate changes in the blood-flow velocity of the ophthalmic artery in patients with endophthalmitis. With pulsed Doppler sonography the blood velocity of the ophthalmic artery was measured in 50 normal subjects and in ten patients with bacterial endophthalmitis. In normal subjects blood velocity decreased with increasing age, and the average systolic/diastolic blood velocity in cm/sec were 38.8 +/- 6.3/11.6 +/- 4.7 in the 18-50-year-old age group and 28.3 +/- 4.6/6.7 +/- 3.3 in the 51-88-year-old age group. Endophthalmitis produced increased systolic/diastolic blood velocity in the ophthalmic artery in the affected eyes in cm/sec (99.7 +/- 15.5/26.6 +/- 10.5 in the 16-50-year-old age group; 60.4 +/- 8.8/16.6 +/- 4.8 in the 51-83-year-old age group). Some patients showed similar changes in the unaffected fellow eyes. The noted elevation of the blood velocity in unaffected eyes may be due to the bilaterally projected parasympathetic fibers of the oculomotor nerve.

Adolescent↗
PubMed1989

[Risk factors for the vis a tergo of the "open eye" in cataract extraction with local anesthesia].

In a prospective study, 244 patients who were scheduled to undergo extracapsular cataract extraction with implantation of the intraocular lens (ECCE/IOL) under local anesthesia were examined to evaluate the risk factors for vis a tergo (VAT) at the "open eye". The intraoperative blood pressure was found to be the most important factor for the occurence of VAT. We think that a reversible suprachoroidal effusion syndrome is responsible for this effect. In order to minimize intraoperative complications, we recommend routine monitoring and treatment if the intraoperative blood pressure is too high during cataract surgery with local anesthesia.

Aged↗
PubMed1988

[Continuous blood pressure monitoring in cataract operations under local anesthesia].

Clinical data of 69 patients due to undergo ECCE with PCIOL implantation were evaluated in a standardized fashion. The preliminary results show that the blood pressure measured preoperatively and intraoperatively necessitated antihypertensive therapy. The averaged systolic blood pressure in the ward was 147.2 +/- 20.4 mm Hg; before retrobulbar anesthesia 159.9 +/- 30.4 mm Hg; after retrobulbar anesthesia 172.6 +/- 24.2 mm Hg; and at the start of surgery 154.2 +/- 18.4 mm Hg. Maximum intraoperative blood pressure was 156.2 +/- 20.7 mm Hg; at the end of surgery it was 144.3 +/- 19.5 mm Hg. In 12 patients (17%), systolic blood pressure higher than 200 mm Hg was measured after retrobulbar anesthesia. Antihypertensive therapy (nifedipine, nitroglycerin) was initiated in 44 patients (64%). These data support the recommendation that blood pressure should be monitored continuously both before and during the operation in order to minimize the rate of surgical and general complications.

Aged↗
PubMed1988

Mepivacaine plasma levels after retrobulbar anesthesia.

Plasma concentrations of mepivacaine were determined after retrobulbar anesthesia. The measured maximal blood levels that can produce systemic side effects range from 1.23 to 4.88 micrograms/ml. We therefore recommend preoperative and intraoperative monitoring of arterial blood pressure and ECG.

Anesthesia, Local↗
PubMed1987

Central administration of benzodiazepines alters water absorption by the rat ileum in vivo.

Two types of benzodiazepine receptors have been identified in the central nervous system. The aim of these experiments was to determine if ligands for these receptors alter basal water absorption by rat ileum in vivo after central administration. Specifically, the effects on net water flux of the systemic and central administration of diazepam and the central administration of RO 5-4864, a "peripheral" receptor agonist, and of the "central" receptor agonists clonazepam and lorazepam were determined. Diazepam increased absorption at 4.3 mg/250 g body wt i.p. but not at 430 micrograms/250 g body wt. Intracerebroventricular diazepam (28 micrograms) increased water absorption. Larger doses had a greater effect. Intracerebroventricular RO 5-4864 (100 micrograms) increased net water absorption; intracerebroventricular lorazepam (50 or 100 micrograms) or clonazepam (100 micrograms) reduced basal water absorption. Systemic atropine (2 mg/kg i.v.) abolished the effect of lorazepam (100 micrograms i.c.v.). To evaluate the possibility that diazepam and RO 5-4864 have effects similar to those of calcium channel antagonists, nifedipine, nitrendipine, and diltiazem were administered intracerebroventricularly. The dihydropyridine calcium channel antagonists nifedipine and nitrendipine increased basal water absorption. Diltiazem, a benzothiazepine compound, did not alter basal water absorption. We conclude that the binding of benzodiazepine agonists to receptors located in the central nervous system alters net water absorption by the rat ileum. Agonists of the central benzodiazepine receptor reduce basal water absorption via a cholinergic neural pathway. Peripheral agonists increase net water absorption. In this model, diazepam behaves as a peripheral receptor agonist. This study provides further evidence of a role for the central nervous system in the regulation of intestinal absorption of water and ions.

Animals↗
PubMed1986

DMO-transport in human red blood cells.

The DMO (5,5-dimethyloxazolidine-2,4-dione) transport was studied in human red blood cells by measuring the 14C-DMO back exchange under self exchange conditions from 14C-DMO labeled cells at 0 degrees C. the unidirectional DMO-flux was linearly related to the DMO concentration up to approx. 100 mM. The unidirectional DMO-flux increases as pH is reduced. The DMO transport is not inhibited by anion transport inhibitors like DIDS, SITS, dipyridamole, phlorhizin, salicylate or butanol. A close correlation between the unidirectional DMO-flux and DMOH, the unionized form of DMO, has been observed suggesting that DMO is transported predominantly by nonionic diffusion. the permeability of DMOH is 9.5 X 10(-6) cm/s (0 degrees C) while the permeability of DMO- cannot be assessed from our data.

Adult↗
PubMedDate not supplied

[TalkingEyes-and-more].

To avoid the clinical manifestation of a vascular disease like stroke it is necessary to detect early vascular signs, to begin a therapy before the outbreak of the vascular disease happens. "TalkingEyes-and-more" is an interdisciplinary and quality-assessed program for prevention of vascular diseases. In several "screening-centers" in Germany interested citized were examined by non-invasive and fast methods to estimate the vascular risk. The examinations were performed on site, the medical evaluation of the data and images were performed centrally in the reading center of the Private Center of Preventive Medicine and Eye Diagnostics" in Erlangen by medical doctors. Alterations of the microvessels become often at first visible in retinal vessels. "TalkingEyes-and-more" examined telemedically the retinal vessels by a patented approach regarding microangiopathic abnormalities. In addition other risk factors like arterial blood pressure, intima media thickness of the carotid artery, cholesterol, fasting glucose, extended bodymass index, and others were documented. By these data a risk index is calculated and a proposal for improving the risk factors is generated.

Adult↗